Communications networks typically incorporate multiple system architectures implementing multiple protocols for the delivery of services such as voice, video and data. For example, the delivery of voice messaging over the Internet using a connectionless format can be more economical than the connection oriented conventional PSTN. To meet user expectations, however, the quality of service provided by an Internet service provider needs to be at least as good as that provided by the PSTN. This can pose a problem for a “best effort” service as typically provided by the Internet.
Accordingly, considerable effort has been, and continues to be, devoted to the development of systems that enable the transport of real time services over connectionless architectures. Asynchronous Transfer Mode (ATM), based on a fixed size cell, is frequently used to provide services where various categories of service can be accommodated. These include real time transmission of voice and video as well as non-real time for services such as data.
MPLS (multi protocol label switching) is a relatively new technology that allocates tags or labels to traffic packets and provides the ability to differentiate classes for individual data flows. The labels are in effect like an address label in a conventional package delivery system. MPLS includes the ability to tunnel through many routing stages and to do so using explicit routing rather than hop by hop routing. When packets enter a MPLS-based network they are given a label or identifier. These identifiers contain routing information such as source, destination, bandwidth and delay criteria.
The mediation of ATM to MPLS requires that cells at the ingress side of the MPLS network be converted to MPLS packets for transport through the MPLS tunnel. At the downstream end of the MPLS tunnel, MPLS packets are converted back to ATM cells for further processing by the downstream ATM network.
A routing switch platform (RSP) such as an Alcatel 7670 RSP includes hardware and software which can provide the mediation function at each end of the MPLS tunnel. The ATM cell to MPLS packet assembly facilitated by the mediation function typically requires that multiple queues be provided for storing connections during the packet assembly or re-assembly process. These queues known, as re-assembly queues, are assigned to connections and in a typical implementation the ratio of queues to connections is low in order to preserve system resources. For effective use of storage resources allocated to the re-assembly queues, a dynamic assignment of the re-assembly queues, is presented in the present invention.
Since ATM to MPLS mediation is a relatively new technology the problem of dynamically assigning re-assembly queues has not been solved in the prior art in as much as the problem has not heretofore arisen. Typically, in connectionless, packet oriented systems such as IP routers, there is a queue per quality of service (QLS) level, per class of service (COS) level or per flow.
In connection-oriented systems such as an ATM switch, there is typically a queue per connection. Mediation applications like the present ATM to MPLS implementation require inter workings of connectionless and connection oriented systems hence queue management problems arise since the queues are assigned differently in the different types of system.
The present invention addresses the aforementioned requirement of providing ATM over an MPLS network and in particular the assembly of ATM cells into MPLS packets for transmission through the MPLS network in an MPLS tunnel in, for example, a packet over sonnet (POS) application. More particularly, the invention is directed to the problem of efficiently using re-assembly queues that perform the cell to packet assembly operation in a communications system. Efficient use of these queues is especially important in cases where the ratio of queues to ATM connections supported by the queues is very low, for example 1:100 as is the case for an OC 48 to POS card on a routing switch platform such as the Alcatel 7670. In a typical application an OC 48 POS card may support up to or more than 100 k ATM connections with only a limited number of re-assembly queues (for example 1024) hence the need to dynamically assign these queues to the ATM connections is apparent.
As indicated previously the prior art does not address the problem since ATM to MPLS mediation is a relative new application.